The olfactory system in animals from Drosophila to humans is able to detect and distinguish among a remarkable number of odors. This ability depends on large and highly diverse families of odor receptors whose members are expressed in subsets of olfactory receptor neurons and which confer upon these neurons their odor specificities. Despite the fundamental role of odor receptors in normal olfactory function, very little is known about the functions of individual receptors in any species. This study will undertake an in vivo analysis of odor receptor function in the Drosophila antenna. The contribution of individual odor receptors to receptor neuron response properties will be examined, thus furthering our understanding of both olfactory coding and the molecular basis of odor-receptor interactions.